linux-kernel - Re: [RFC] Bluetooth: Retry configure request if result is L2CAP_CONF

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Message-Id: <3E87E315-0F39-49BA-BD65-2EB0C3A9A782@holtmann.org>
Date:   Mon, 18 Feb 2019 13:58:45 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     linux-bluetooth@...r.kernel.org,
        "Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>,
        Florian Dollinger <dollinger.florian@....de>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] Bluetooth: Retry configure request if result is
 L2CAP_CONF_UNKNOWN

Hi Andrey,

> Due to:
> 
> - current implementation of l2cap_config_rsp() dropping BT
>   connection if sender of configuration response replied with unknown
>   option failure (Result=0x0003/L2CAP_CONF_UNKNOWN)
> 
> - current implementation of l2cap_build_conf_req() adding
>   L2CAP_CONF_RFC(0x04) option to initial configure request sent by
>   the Linux host.
> 
> devices that do no recongninze L2CAP_CONF_RFC, such as Xbox One S
> controllers, will get stuck in endless connect -> configure ->
> disconnect loop, never connect and be generaly unusable.
> 
> To avoid this problem add code to do the following:
> 
> 1. Store a mask of supported conf option types per connection
> 
> 2. Parse the body of response L2CAP_CONF_UNKNOWN and adjust
>    connection's supported conf option types mask
> 
> 3. Retry configuration step the same way it's done for
>    L2CAP_CONF_UNACCEPT
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> Cc: Pierre-Loup A. Griffais <pgriffais@...vesoftware.com>
> Cc: Florian Dollinger <dollinger.florian@....de>
> Cc: Marcel Holtmann <marcel@...tmann.org>
> Cc: Johan Hedberg <johan.hedberg@...il.com>
> Cc: linux-bluetooth@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
> 
> Everyone:
> 
> I marked this as an RFC, since I don't have a lot of experience with
> Bluetooth subsystem and don't have hight degree of confidence about
> choices made in this patch. I do, however, thins is is good enough to
> start a discussion about the problem.

can you take a btmon -w trace.log protocol trace so that I can see where it fails. This seems a really odd behavior of the Xbox controller. We have to be careful in not breaking Bluetooth qualification to just workaround some buggy remote device.

Regards

Marcel